I have recently had my Vrs re-mapped by Impossible Performance, and since then something odd has been happening with the secondary air pump. I think however that it is just a coincedence.

When the car is started from cold, the air pump kicks in for a while making the exhaust sound a bit throaty, this is normal. But since the remap, every now and then the pump kicks in again for a few seconds, usually when idling, making it sound like the air filter has fallen off, then it returns to normal. This happens at random times during each journey.

There is no loss of performance and economy is the same, so I was thinking that there may be a sensor on the blink.

What tells the pump to turn on? Am I right in thinking it is the temperature sensor and O2 sensor? Are these worth changing anyway? What else could cause it, MAF, dirty throttle housing?

TIA

it's the coolant temperature sennsor which tells the auxillary air pump to switch on and off.....

it could be either because the sensor is naff or that something is causing the coolant temperature to go up and down like a dodgey thermostat or an air lock in the cooling system or similar

I think that the upstream O2 sensor also affects whether the 2ndary airpump is active - I'm not sure how the temp sensor plays a role..

12v Pages - The Engine - How it Works

I had an over-active pump and it was improved by cleaning throttle body and airpump.

the whole reason the auxillary air pump is there is to reduce the exhaust emmssions on start up by pumping cold air into the exhaust system, it gets a signal from the ecu to the pump relay, and this is based on the coolant temperature and a few other things

ive just read this post and mine does this to!! and mine has not been mapped yet so it must be coincidence on yours.

What was the final outcome on this fault, matter?

Thanks for your help guys. I have bought a new CTS today at a quite-expensive-for-what-it-is £24. Lets hope it cures the problem.

Ended up buying an upper and lower S3 brace too while I was there, this tuning malarky is becoming expensive!

has it solved the problem? and where is it on the vrs?

thanks, i will be doing mine soon if its not to dificult!!